After-effect of photoperiodism in relation to development and yield of rice plant : (III) Effect of growth and time of heading of rice plant.

In the preceding paper, we reported on the premature heading caused by short-day treatment in seed-bed stage, with reference to the premature heading inductivity of the rice plant. Both in pot- and in field-experiments it was observed that the short-day treatment resulted in not only a induction of premature heading, but also delaying of the natural heading in the later period, in cases where the premature heading inductivity being large, the heading is much delayed. The long-day treatment combined with short-day seems to concel the delay of heading, although the effect of long-day alone was not always remarkable. The short-day treatment caused an increase in plant height and a decrease in number of tillers, in seed-bed, as compared with control plants. After transplantation a gradual decrease in height-growth and increase of number of tillers was observed. But the growth became vigorous again after the premature heading, and at the final stage the plant was slightly higher and evidently more tillers than the control plants. On the other hand the long-day treatment resulted in the lower plants having many tillers in seed-bed, but after transplantation the plant height increased and no more difference was observed between the treated and the control except the number of tillers was slightly few.